A circular wire of length 0.1 m is touching the surface of the liquid of surface tension ` 3 xx 10^(-2)` N/m The mass of a wire is `10^(-4)` kg . If g = 10 `m//s^(2)` then the force needed to lift the circular wire is

Options

A. `7xx10^(-3)`N
B. `0.7 xx 10^(-3)`N
C. `0.07 xx 10^(-3)`N
D. `70 xx 10^(-3)` N

Answer

A

Explanation

`F = mg + T xx 2l = 10^(-4) xx 10 + 3 xx 10^(-2) xx 0.2 `
` = 1 xx 10^(-3) + 6 xx 10^(-3) = 7 xx 10^(-3)` N